Since we have a long running discussion about gay characters in a lords & ladies setting, I figured a constructive thread discussing ways to do a server that is open to alternatives for lords & ladies would be a good idea.
Let's start by establishing a baseline. The bog standard L&L setting is heavily patriarchal, is monogamous or polygynous, has political power held entirely or almost entirely by male characters, and has bloodline being tied to political power.
As the central conceit of the lords & ladies genre of MU*s is that there is a class-system in the setting, suggestions should aim to maintain that aspect of the lords & ladies veneer, meaning that a peerage exists within the setting and that the right to rule is somehow maintained in a verisimilitudinous/believable manner. An idea for a server with a classless society would not fit with the discussion; though, it might still be an interesting server idea to pursue.
Discussion should be constructive, as this is not the Hogpit, and should focus on how suggestions could be made better, on inconsistencies, on interesting offshoots or elaborations to an idea, on the verisimilitude/believability of the system, on blindspots the the writer might not be aware of in their idea, etc.
I'll start. These will just be quick rundowns rather than full explorations of the ideas.
Matrilineal, non-matrimonial society. Political power and titles are passed down solely through mothers to their children. Marriage doesn't exist. No one cares who your father is. A prince could become the king because his mom is the queen. His children won't inherit his political title all. His sister's children would. The prince, as a king, would not have a queen consort.
Matrilineal, matrimonial society. Same as above but there is marriage, likely only for political reasons. A prince could become the king because his mom is the queen. The king consort might be his father or might not. Maybe his father was the hunky stablehand the queen had a dalliance with before she was married. It doesn't matter. The prince, once he is king, could marry someone, male or female, but the ones who will inherit his title would, again, be his sister's children not his.
Spouses and consorts/concubines. Spouses are partners who are peers or are peers of roughly the same rank. Consorts/concubines are partners who are commoners or commoners and peers of significantly lower rank. Children of spouses have the highest legitimacy to inherit, but children of consorts/concubines also can inherit if there are no spousal children or perhaps can inherit in other circumstances to be defined by the setting. Heirs can be adopted and take the same rank as children of consorts/concubines.
Authority equals ass-kicking. This is the most metal/badass option for a lords & ladies game. Might makes right...to rule. The king/queen doesn't wear a crown; they wear a title belt. The king/queen isn't the king/queen because of who their parents are; they're king/queen because they kicked the ass of the previous king/queen and no one else has been able to take the title from them yet. No one cares who marries who or whose children are whose. This might work in a shonen lords & ladies game or maybe a very high magic setting where the king/queen is the strongest sorcerer in the land and all the dukes/duchesses, counts/countesses, and barons/baronesses are progressively weaker wielders of magic.